The side tanks on mine a definitely soldered on.

The solder melted pretty easily with a gas torch. I think I am going to TIG the pipes and temp sensor fitting on so I can solder the tanks back on and not worry about disturbing them.

I wonder if this was done to ease repairs? Larry's HRC radiator has all three TIG, gas weld and solder! I have heard the factory A-Kit and HRC RS's are similar.
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Andre E. Benguerel
1996 Honda NSR250R
Daijiro Kato/Fortuna Replica #74

2000 Honda RS250R (NX5)
2008 Honda RS250R (NXA)
AFM Expert #430